[PATCH AUTOSEL 6.14 227/642] tcp: bring back NUMA dispersion in inet_ehash_locks_alloc()

Sasha Levin
2025-05-05T22:23:29Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit f8ece40786c9342249aa0a1b55e148ee23b2a746 ]

We have platforms with 6 NUMA nodes and 480 cpus.

inet_ehash_locks_alloc() currently allocates a single 64KB page
to hold all ehash spinlocks. This adds more pressure on a single node.

Change inet_ehash_locks_alloc() to use vmalloc() to spread
the spinlocks on all online nodes, driven by NUMA policies.

At boot time, NUMA policy is interleave=all, meaning that
tcp_hashinfo.ehash_locks gets hash dispersion on all nodes.

Tested:

lack5:~# grep inet_ehash_locks_alloc /proc/vmallocinfo
0x00000000d9aec4d1-0x00000000a828b652 69632 inet_ehash_locks_alloc+0x90/0x100 pages=16 vmalloc N0=2 N1=3 N2=3 N3=3 N4=3 N5=2

lack5:~# echo 8192 >/proc/sys/net/ipv4/tcp_child_ehash_entries
lack5:~# numactl --interleave=all unshare -n bash -c "grep inet_ehash_locks_alloc /proc/vmallocinfo"
0x000000004e99d30c-0x00000000763f3279 36864 inet_ehash_locks_alloc+0x90/0x100 pages=8 vmalloc N0=1 N1=2 N2=2 N3=1 N4=1 N5=1
0x00000000d9aec4d1-0x00000000a828b652 69632 inet_ehash_locks_alloc+0x90/0x100 pages=16 vmalloc N0=2 N1=3 N2=3 N3=3 N4=3 N5=2

lack5:~# numactl --interleave=0,5 unshare -n bash -c "grep inet_ehash_locks_alloc /proc/vmallocinfo"
0x00000000fd73a33e-0x0000000004b9a177 36864 inet_ehash_locks_alloc+0x90/0x100 pages=8 vmalloc N0=4 N5=4
0x00000000d9aec4d1-0x00000000a828b652 69632 inet_ehash_locks_alloc+0x90/0x100 pages=16 vmalloc N0=2 N1=3 N2=3 N3=3 N4=3 N5=2

lack5:~# echo 1024 >/proc/sys/net/ipv4/tcp_child_ehash_entries
lack5:~# numactl --interleave=all unshare -n bash -c "grep inet_ehash_locks_alloc /proc/vmallocinfo"
0x00000000db07d7a2-0x00000000ad697d29 8192 inet_ehash_locks_alloc+0x90/0x100 pages=1 vmalloc N2=1
0x00000000d9aec4d1-0x00000000a828b652 69632 inet_ehash_locks_alloc+0x90/0x100 pages=16 vmalloc N0=2 N1=3 N2=3 N3=3 N4=3 N5=2

Signed-off-by: Eric Dumazet <edumazet@google.com>
Tested-by: Jason Xing <kerneljasonxing@gmail.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250305130550.1865988-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv4/inet_hashtables.c | 37 ++++++++++++++++++++++++++-----------
1 file changed, 26 insertions(+), 11 deletions(-)

diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 9bfcfd016e182..2b4a588247639 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -1230,22 +1230,37 @@ int inet_ehash_locks_alloc(struct inet_hashinfo *hashinfo)
{
unsigned int locksz = sizeof(spinlock_t);
unsigned int i, nblocks = 1;
+ spinlock_t *ptr = NULL;

- if (locksz != 0) {
- /* allocate 2 cache lines or at least one spinlock per cpu */
- nblocks = max(2U * L1_CACHE_BYTES / locksz, 1U);
- nblocks = roundup_pow_of_two(nblocks * num_possible_cpus());
+ if (locksz == 0)
+ goto set_mask;

- /* no more locks than number of hash buckets */
- nblocks = min(nblocks, hashinfo->ehash_mask + 1);
+ /* Allocate 2 cache lines or at least one spinlock per cpu. */
+ nblocks = max(2U * L1_CACHE_BYTES / locksz, 1U) * num_possible_cpus();

- hashinfo->ehash_locks = kvmalloc_array(nblocks, locksz, GFP_KERNEL);
- if (!hashinfo->ehash_locks)
- return -ENOMEM;
+ /* At least one page per NUMA node. */
+ nblocks = max(nblocks, num_online_nodes() * PAGE_SIZE / locksz);
+
+ nblocks = roundup_pow_of_two(nblocks);
+
+ /* No more locks than number of hash buckets. */
+ nblocks = min(nblocks, hashinfo->ehash_mask + 1);

- for (i = 0; i < nblocks; i++)
- spin_lock_init(&hashinfo->ehash_locks[i]);
+ if (num_online_nodes() > 1) {
+ /* Use vmalloc() to allow NUMA policy to spread pages
+ * on all available nodes if desired.
+ */
+ ptr = vmalloc_array(nblocks, locksz);
+ }
+ if (!ptr) {
+ ptr = kvmalloc_array(nblocks, locksz, GFP_KERNEL);
+ if (!ptr)
+ return -ENOMEM;
}
+ for (i = 0; i < nblocks; i++)
+ spin_lock_init(&ptr[i]);
+ hashinfo->ehash_locks = ptr;
+set_mask:
hashinfo->ehash_locks_mask = nblocks - 1;
return 0;
}
--
2.39.5